1. Field of the Invention
This invention relates to a nonvolatile semiconductor memory device and a method for manufacturing the same, and more particularly to a nonvolatile semiconductor memory device with a plurality of dielectric films and electrode films alternately stacked on a substrate, and a method for manufacturing the same.
2. Background Art
Recently, to increase the density of flash memory, a technique for multilayering cells has been developed. In this technique, dielectric films and electrode films are alternately stacked on a substrate, and then through holes are simultaneously formed therein. A charge storage layer for retaining charge is formed on the side surface of the through holes, and a columnar electrode is buried inside each through hole. Thus, memory cells are three-dimensionally arranged at the intersections between the columnar electrodes and the electrode films. Then, a plurality of select gate lines extending in one direction are provided on the uppermost electrode film, and a plurality of bit lines extending in another direction are provided thereabove and connected to the upper end portion of the columnar electrodes, so that any of the columnar electrodes can be selected. On the other hand, each electrode film is connected to a different one of word interconnects so that any of the electrode films can be selected. This enables any of the memory cells to be selected for writing and reading data (see, e.g., JP-A-2007-266143(Kokai)).
However, in such a stacked flash memory, with the advance of downscaling, the amount of charge stored in each memory cell decreases and causes the problem of decreased reliability.